On the matter of the genetics of magical ability in the Harry Potter universe.

So the first thing I’ll illustrate will be my personal hypothesis regarding magical genetics.

I have spent a lot of time thinking about this. Partially because I have no life and am a sad, lonely individual on Friday nights and weekends, and partially because Rowling seems to not know her genetics at all (even if some of her fans do) and I can’t really control myself when I see a wrong that I feel should be righted. It brings me a personal peace of mind to be able to explain exactly what was going on.

Now, frankly I could just link to Ms. Klenotiz and leave it at that. She’s clearly more well-versed in her understanding of genetics than I am, but I have a few issues with her model. See, a proper theory of magical genetics within the Harry Potter universe needs to explain several things:

1.) Muggleborns

2.) Squibs.

3.) The rarity of wizards (as well as the rarity of muggleborns and squibs within the already frightfully small wizarding world). 1

4.) The varying levels of magical power to be found in different wizards.

5.) How a character’s relative “blood purity” does not in any way predict how powerful they are.2

Ms. Klenotiz easily manages to tackle the first two, glances over the third and kinda sorta tackles the fourth, but she doesn’t give the fifth justice. By her hypothesis, wizards whose parents were wizards(and grandparents, and so forth) should by all means be much more powerful than the average mudblood, what with all those trinucleotide repeats and genetic anticipation.

I have a hypothesis that I think manages to cover all the data. Sadly, it’s far more complicated than Ms. Klenotiz’s own, but I think that is forgivable given the aforementioned rarity of wizards. If more and more things have to come together in order for one wizard to be born, it’s less far-fetched that they are so astonishingly rare.

My hypothesis:

There are multiple magical genes, three in fact.

One allows for perception of the magical world (ability to see ghosts and dementors and being able to shrug off anti-muggle charms, etc), and because it’s perception, we’ll call it P. Except it’s a recessive gene, so we’ll give it a little “p”. You need two little ps for it to work.

The second allows for manipulation of the magical world (spells, moving things with your mind, flying brooms, so forth), and this gene is dominant, as Rowling said (presumably this is the gene she was referring to), and so we give it a capital “M”, for manipulation. The manipulation gene is epistatic. So it needs both the activation gene and the perception gene to function, else it becomes dormant, and now you just have a carrier. You only need to have one of these.

The third is the activation gene. It activates the manipulation gene and the perception gene. This is a recessive gene as well, and because of that we give it a little “a”. You need two of these.

Then you make a punnet square, because as an uninformed member of society regarding the finer points of genetics, I didn’t really take non-mendelian genes into account when I was making my theory. I just kind of made up a hypothetical hormone and a few other things. So thanks to this lovely punnet square calculator, you can check it out if you want. Get your A, a, P, p, M, and m.

So if you pay attention to this, you’ll see how there’s this tiny purple square at the bottom that says aappmm, and it has three dark blue squares around it. The purple square represents the squib pregnancies, the dark blue squares represent the wizard pregnancies.

So, by this standard, 1/64 pregnancies in the world is a squib(ish), and 3/64 are wizards(ish again, because statistics).

Now, before we get into the math, let me explain in a little bit more depth how I envision these genes working.

First, the manipulation gene, or the magic gene, is one that allows the body to create what I like to call merlinin. Why merlninin? Because everybody knows Merlin, and I’m feeling lazy with my hormone naming3. Merlinin allows humans’ intents, thoughts, and emotions to manifest in the physical world, however it doesn’t do this on its own. If you were to inject a muggle with a bunch of merlinin, unless they were a very specific kind of carrier, they would probably just let it go to waste.

The activation gene, besides letting the manipulation gene do its thing, also allows for a neurotransmitter which I will call thaumatocin (because why not? Greek word for wonder, seems fitting). Now what thaumatocin does is that it lets your brain tell your merlinin to do things, which manifests in magic.

However, now that this is clarified, you go over to the perception gene, that allows people to have what I call merlinin receptors. Which, as the carefully-chosen name should indicate, are the thingies in the body that allow it to take in merlinin(as well as be susceptible to magical stimuli and magical diseases, which I’ll get to in a bit). What this means is that you may have all the thaumatocin and merlinin that you want, but if your body can’t tell that there’s merlinin there, it can’t send the signal properly. This means that the theoretical person with magical powers who is unaware of them due to not having the perception gene can’t exist4.

Also presumably wizards have some sort of super-powerful telomeres or some innately better telomerase which allows them to live so freakishly long and withstand all that running about and flying and teleporting at the young age of 1155. However I haven’t fully figured out how that’s supposed to work beyond “magic”.

Now, a separate yet relevant hypothesis I have regarding the rarity of wizards is that maybe evolution had something to do with it. Why in the name of Charles Darwin would wizards be less likely to survive than muggles in the wild? I am of the personal belief that wands are a very recent invention. Perhaps not from the viewpoint of a human lifetime but definitely so from the viewpoint of evolution. Back in caveman times, wizards did not have spells, and they did not have apparition, and they did not have flying brooms or other magical objects. Something they did have, though, was illnesses. While in modernity, with the relatively sanitized world we live in, it seems strange to think that magic may have been a detriment instead of a boon in terms of survival, muggles have been shown to be completely immune to magical diseases. There are no muggles with Dragon Pox, or Spattergroit, or any magical diseases in sight. Presumably this immunity helped them not die and have lots of sex. And this, ladies and gentlemen, leads into why the ratio of wizards-to-muggles shrinks from 3/64 to anywhere between 1/512 to 1/2000 (lets say the books are vague, and leave it at that, to keep my internal ragemonster in its cage).

See, given my hypothesis 4/64(or 1/16) of all babies should be able to perceive the magical world, however this does not hold up with the data. Wizards and squibs are not 1/16, though they might be 1/1600. The reason for this may be the aforementioned muggle immunity to magical illnesses.

Given that there are so few wizards, and so many muggles, it would seem strange that muggleborns are considered a minority and not a majority of wizards. Think about it, if we assume there’s 1,000 wizards, and there’s 100,000 muggles (which is actually a very liberal estimate. Wizards should be far less than 1% of the population), assuming no squibs, and even assuming a healthy birth rate (that wizards do not have, most purebloods are only children) and that everyone has children, you’d have approximately 2,000 magical pureblood babies, and over 4,000 muggleborn babies. It makes no sense. Add to that something closer to the actual ratio like 1/512, which is still not that close to the books but it seems like a vaguely helpful compromise, if 512,000 muggles have kids, they have 1,000 wizards, while the 1,000 wizards have 2,000 kids…

That is unless 3/64 pregnancies are magical, but only 1/24 of those actually carry to term.

Now, autoimmune disorders are one of the most common reasons for miscarriages, and given muggles’ natural immunity to magical illnesses, it would not be far-fetched to think that 23/24 muggleborn fetuses are not born either because the mother was exposed to a magical illness that killed the child but never harmed her, or because the mothers’ body identifies the magical child as a magical parasite and, uh… treats it as such.

Thank you for reading my hypothesis, now go on and give Ms. Klenotiz’s a try if you haven’t read it yet. I think mine fits the data better, but hers is more thoroughly researched.

Lastly, Ms. Klenotiz, if you’re reading this, what do you think?

1 I’m looking at you Eliezer S. Yudkowsky. Squibs are not that frequent. I know you’re a genius and I am just a mere mortal, but your hypothesis is not supported by the data. When that happens, you don’t change the data, you change your hypothesis. I’ve had to change mine several times, it’s not that hard.

2 In fact most notably powerful wizards are classified as halfbloods (McGonnagal, Dumbledore, Harry, Voldemort, Snape…), some are muggleborn (Hermione, Lily Evans…) and a few are pureblood (Bellatrix, Mad Eye, Slughorn, um, er… Neville maybe?) while there are also many non-exceptional half-bloods, muggleborns, and pure-bloods. Heck, look at the list for a while, it could seem that being pure-blooded is actually bad for your magical adeptness. Crabbe, Goyle, Flint, Malfoy, Umbridge, the Weasleys aren’t all that badass either, with exception of that one scene where Mrs.Weasley lets all that motherly fury out and becomes the most memetically badass character in the whole series by killing Bellatrix.

3 If Calcitonin is good enough for doctors, Merlinin is good enough for me.

4 They can’t, because they don’t, there’s no data for them to exist, nearly everyone who has seen my hypothesis has pointed out that it would be cool, but it doesn’t work. Please don’t send me hundreds of emails about that. It’s not a hole in the theory.